Abstract: Objective:To explore the therapeutic effect of naloxone on the treatment of chronic obstructive pulmonary disease(COPD) complicated with type Ⅱ respiratory failure.Methods:Sixty-nine consecutive patients with COPD complicated with type Ⅱ respiratory failure were randomly divided into two groups:control group and therapy group.Thirty-four patients were in control group,16 of them had pulmonary encephalopathy.They were received conventional therapy.While 35 patients were in therapy group,18 of them had pulmonary encephalopathy.In therapy group,1.0 mg of naloxone and 20 ml normal saline were intravenously infused twice one day in addition to conventional treatment,6 days for a course of treatment.The recovery time of pulmonary encephalopathy and the changes of blood gas analysis in the two groups were observed.Results:There was significant improvement in therapy group about the recovery time of respiratory failure and pulmonary encephalopathy and the improvement of blood gas analysis compared to control group(P0.05-P0.01).Conclusions:Naloxone has the significant therapeutic effect in treatment of COPD complicated with type Ⅱ respiratory failure.